Hemimercaptals



Patented July 17, 1951 HEMIBIERCAPTALS Frank Kipnis, Morris Plains, andJohn Ornfelt,

Morristown, N. J assignors, by mesne assignments, to American HomeFoods, Inc., New York, N. Y.,' a corporation or New Jersey No Drawing.Application August 22, 1947, Serial No. 770,178

8 Claims.

This invention relates to certain hemimercaptals having useful aromasand odors, and to a method of producing them. More particularly itrelates to hemimercaptals resulting from the condensation of a moleculeof a substituted glyoxal with a molecule of a mercaptan free ofsolubilizing groups and their immediate deriva tives.

Many reactions of carbonyl compounds with mercaptans have been reportedin the chemical and patent literature. For example, Schubert (J. Biol.Chem., 111 (1935), 671) reported on the interaction of methyl and phenylglyoxal with thiol acids such as thioglycolic acid, and theirderivatives and with thiourea. The reactions, carried out in aqueous oralcoholic media, yielded compounds of importance in biochemical theorybut not of value for their aromatic or olent properties; additionproducts and condensation products were formed, among the latter being asubstituted thiazolidine carboxylic acid from cysteine. Martin et a1. (U.8. Patent 2,223,693, December 3, 1940) describe the reaction ofaldehydeor keto-sulfonic acids with mercaptans to form water-solublethioacetalsulphonic acids. They state that while a number of notsulphonated thioacetals have been obtained by reaction of mercaptans onketones and aldehydes in presence of acid condensing agents, thereaction takes place plainly or smoothly with simple monoaldehydes andmonoketones only. Schirm (U. S. Patent 2,369,612, February 13, 1945) discloses broadly the possibility of condensing carbonyl compounds withmercaptans to produce mercaptals or mercaptols; specifically hedescribes the reaction of paraformaldehyde with cetylmercaptan to giveformaldehydedicetylmercaptal; monochloroacetal with n-octylmeroaptan togive chloroacetaldehydedioctylmercaptal; glucose with dodecylmercaptanto give glucosedodecylmercaptal; and levulinic acid withoctadecylmercaptan to give di-octadecyhnercaptovalerlanic acid. Allthese reactions were catalyzed by hydrogen chloride.

As will be obvious from an inspection of the structural formulas:

there are numerous possibilities in the reaction of a mercaptan with apolycarbonyl compound.

2 The most probable are the formation 01' mercaptals and mercaptols (I),and hemimercaptals and hemimercaptols (II):

s-n" a-o 0-0 11 and but numerous by-reactions, as well as reaction ofthe mercaptan with a second carbonyl group, are not excluded. Suchcondensations have in general been carried out in the presence of anacid oatalyste. g. hydrogen chlorideand the course is ordinarily notsimple. As pointed out by Martin et a1. (quoted above) the reaction wasexpected to go smoothly only in the case of monoaldehydes andmonoketones, in the presence 01' acid condensing agents.

Contrary to this expectation we have discovered that with a selectedgroup of reactants hemlmercaptals are formed in high yield without theuse of any condensing agents and without the necessity of using anextraneous reaction medium such as water, alcohol or other solvent; thereaction proceeds smoothly with the formation of a negligible amount ofmercaptals or other byproducts, and such by-products as are formed arereadily separable from the hemimercaptals. We have further discoveredthat the hemimercaptals thus produced have marked odors and aromas, manyof them being similar to those of food products or of non-food plantmaterials; accordingly, in addition to constituting a new series ofstarting materials for organic syntheses, they should be of value invarious industrial fields, for example as ingredients in scents forsoaps and the like, in animal baits and in flavoring materials.

One of the objects of our invention is to pro vide certainhemimercaptals having desirable aromatic and olent properties.

Another object of our invention is to provide certain hemimercaptalswhich will serve as new starting materials for organic chemicalsyntheses.

A further object of our invention is to provide 3 a method of synthesis01 certain hemimercaptals which is economical and efficient and does notrequire the use of a condensing agent.

Additional objects and advantages 01' our invention will be apparent tothose skilled in the art from the iollowing description.

According to our invention we cause a substituted glyoxal having theformula R'OO-OO-H to react with a mercaptan having the formula H-B-R', Bbeing an alkyl, carbocyclic or heteroeyclic radical, and B being analkyi, carbocyclic or heterocyclic radical containing no solubilizinggroup; R and R may be the same of diflerent. By "solubilizing group wemean such groups as CO:H, --SOaH, NH2, which render the compounds inwhich they are found soluble in water or in aqueous acids or alkalies.

In carrying out the reaction we mix molar equivalents of the selectedglyoxal and mercaptan and stir the mixture. No condensing agent is addedand the use oi a reaction medium such as a solvent is unnecessary andpreferably avoided. In most cases the condensation reaction beginsspontaneously with the development of considerable heat; as the reactionproceeds the temperature rises to a maximum and then gradually falls asthe reaction is completed. on standing at room temperature the reactionmixture solidifies to a crystalline mass oi crude hemimercaptal whichmay be purified by recrystallization from a suitable solvent, e. g. ahydrocarbon fraction. In some cases it may be desirable to initiate thereaction by gentle heating and in some cases external cooling at theheight of the reaction may be desirable, but in most cases no preheatingor temperature control is needed. The reaction may be represented asfollows:

Examples of the substituted glyoxals that may be thus reacted are:

Piisnylgiyomi lit p-Ethoryphenyiglyonl Thiophenea-giyunlFuryl-ii'giyoxal Amon the mercaptans which may be used are:

Methyl mercaptan H's-C R;

Ethyl mormpian H-S-Cdh n-Propyl mercaptm p-Orssyl moreapilnFuryl-Z-methyl morcaptan lI-B-Clir- \B Thioplicne-z-meth yl mercaptanNsplithyl-i! nmmptan The hemimercaptals of our invention aresubstantially colorless crystalline solids. In solid form they arestable up to their melting points. but on heating in solution. even in anon-polar solvent, they appear to dissociate since the solutions acquirea fairly strong yellow color indicative oi the presence of a glyoxal; oncooling the heated solution the color disappears and the mmimercaptaimay be recovered from the solu- The following examples are illustrativeand not to be taken as limiting our invention, the scope or which isdefined in the appended claims.

EXAMPLE I Thiophena-Z-glyoml-n-propyl hemimercaptal Fourteen grams (0.1mole) thiophene-2-glyoxai was mixed with 1.8 g. (0.1 mole) n-propylmercaptan in an Erlenmeyer flask. A considerable amount 0! heat wasgenerated, the temperature rising to a maximum or about 60 C. in a fewminutes. During the reaction the mixture was occasionally stirred. Afterabout twenty minutes from the initial mixing the temperature had fallento 20 C. Alter the mixture had been allowed to stand for thirty minuteswithout stirring, it solidified to a crystal mass which was freed ofmother liquor and dissolved in hot hexane, from which it crystallized oncooling. The yield was 18.8 g. or 87 percent of the theory. The productconsisted of white crystals which melted with decomposition at 69 C. Acombustion analysis the following results: Calculated i'or CnHzoOaBa:6-49.9795; H--5.59%; 8-29.8495. Found: C--50.53%; H6.01%; B29.72%. Thecompound had an onion odor.

6 The following list gives data on compounds embodying this inventionand made according to the method of this invention.

hemimercnptal. hernimercaptal hemimermptal hemlmercaptal.

crushed herbs, went onion. mild coconut. indefinite, musty. very slight.aromatic sulfur. cooked meat. slight aromatic; bland. cofl'ee (in lowconcentration). fikei meat. I

y; owery; mar gold. cooked cabbage.

Thlophene-2glyoxal-n-propyl hemimercaptal. 09 strong onion.Thlophene-lglyoxal-benzyl hemimercaptal. 78-0 iried onion.'lhiophene-z-glyoxali-naphthyl hemimercaptal 98-9 beef broth.'Ihiophene-zglyoxal-ililophenezmethyl hemimercaptal 5 -5 coilee (iniowconcentratioo Thiophene-2-glyoxal-u-dodecyl hemimercaptal 80-1 mild;roasted meat. Thiophene-Z-glyoxal-phenyi hemimercaptal... 65-6 cookedmeat. Thiolphene 2-glyoxal n-octadccyl hemimercapta 91 slight. pEtoxyphenylglyoxal-ethyl hemimercapta 87-9 grassy.p-Ethoxyphenylglyoxatthiophene-Zmcthyl hemimercaptal- 37-8 coflee (inlow concentration). p-Ethxyphenylgiy0xal-n-d0decyl hemimermptal 65-6mild. p-Ethoxyphenylglyoxal-phenyl hemimeruiptal 67-8 cooked meat. EJEthoxyphenylgIyoxal-benzyl hernimercaptal. 64-5 mild mercaptan.

uryl-2-glyoxal-n-propyi hemimercaptal 105-6 onion. Furyl-zglyoxal-benzyihemimercaptal 103 mild mercsptan. Furyl-itgiyoxatn-dodecyl hemimercaptal106-6 mild. Furyl-2-glyoxal-n-hexyl hemimercaptel C HHOaH -5- 6 wheat.

NOTE: All compounds are colorless crystals.

EXAMPLE II Furyl-Z-glyoxal-n-propyl hemimercaptal Twelve and four-tenthsgrams (0.1 mole) of furyl-Z-glyoxal was mixed thoroughly with 7.6 g.(0.1 mole) of n-propyl mercaptan. The mixture warmed spontaneously, and,on standing for forty minutes, deposited a mass of crystalline material.This could be recrystallized from heptane without further treatment togive a product weighing 19.6 g. (98% yield) and melting at 105-6 C. Ananalysis gave the following results: Calculated for Cam-i038: C53.98%;H6.04%. Found: C53.93%; H6.l4%. The compound had an onion odor.

EXAMPLE III p Ethoxyphenylglyoxal thiophene 2 methyl hemimercaptalEXAMPLE IV Phenylglyoxal-p-naphthyl hemimercaptal Thirteen andfour-tenths grams (0.1 mole) of phenylglyoxal was mixed with 16 g. (0.1mole) of fl-naphthyl mercaptan. Heat was generated and the mixturecrystallized after a short period. On recrystallization from heptane,21.8 g. (74% yield) of product meltin at l-6 C. was obtained. Ananalysis gave the following results: Calculated f0! Ciel-114023:C73.44%, H-4.79%. Found: C72.'l1%; H4.88%. The compound had a pleasantaromatic odor.

80 From the above description it will be evident that we have discovereda new and useful group of hernimercaptals and a surprisingly simple andeflicient reaction for producing them in high yield without the use of acondensin agent.

in which R and R are radicals selected from the class consisting ofalkyl, aryl, aralkyl, alkaryl, alkoxyaryl, furyl, thienyl, alkyl iuryland alkyl thienyl radicals, said hemimercaptals being solid,substantially colorless chemical individuals of well defined crystalhabit.

2. Thiophene 2-glyoxal n propyl hemimercaptal.

3. Phenylglyoxal-B-naphthyl hemimercaptal.

4. p Ethoxyphenylglyoxal thiophene 2- methyl hemimercaptal.

5. Thiophene 2 glyoxal thiophene 2- methyl hemimercaptal.

6. Thiophene 2 glyoxal phenyl hemimercaptal.

'7. The method of forming hemimercaptals which comprises: mixing insubstantially equimolecular amounts under non-aqueous conditions and inthe absence of added condensing agent a glyoxal having the formula:

0 0 Rail-H and a mercaptan having the formula:

H-S-R in which R and R are selected from the class consisting of alkyl,aryl, aralkyl, alkaryl, alkoxyaryl, furyl, thienyl, alkyl furyl andalkyl thienyl radicals. permittin the temperature to rise to a maximumand fall to room temperature, whereby a crystalline mass is formedcontaining the desired hemimercaptal, and recovering 75 saidhemimercaptal from the crystalline mass.

8. The method as defined in claim I, in which UNITED PATENTS 3;iiiyfiififiiaitfinffi i fiy'oflmi 23333 3g3 9 23 W Emma 6 I 2,827,966Morey Aug. 24, 1943 JOHN ORNFELT. OTHER REFERENCES EEEEEENEEE EEEED8233153 2533333 3:: :33; 33:31

The following references are of record in the tile of this patent: l0

1. HEMIMERCAPTALS HAVING THE FORMULA: